Semiconductor photoelectrically sensitive device with low sodium concentration

ABSTRACT

A semiconductor device including a conductive substrate or a first conductive layer formed on the substrate, a non-single-crystal semiconductor layer member is disposed on the conductive substrate or the conductive layer, the non-single-crystal semiconductor layer member having at least one intrinsic, non-single-crystal semiconductor layer, and a second conductive layer disposed on the non-single-crystal semiconductor layer. The intrinsic non-single-crystal semiconductor layer contains sodium and oxygen in very low concentrations where each concentration is 5×10 18  atoms/cm 3  or less.

RELATED APPLICATIONS

This is a divisional application of Ser. No. 07/694,406, filed May 1,1991, now U.S. Pat. No. 5,391,893, which itself is aContinuation-in-part of Ser. No. 06/860,441, filed May 7, 1986, now U.S.Pat. No. 5,043,772, which in turn is a continuation-in-part ofapplication Ser. No. 06/800,694 filed Nov. 22, 1985, now U.S. Pat. No.4,690,717. This application is also related to application Ser. No.525,459 filed Aug. 22, 1983, now U.S. Pat. No. 4,591,892.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements in or relating to asemiconductor photo-electrically-sensitive device which has at least anon-single-crystal semiconductor layer member having at least oneintrinsic non-single-crystal semiconductor layer.

2. Description of the Prior Art

Heretofore there have been proposed a variety of semiconductorphoto-electrically-sensitive devices of the type that have at least onenon-single-crystal semiconductor layer member having at least oneintrinsic non-single-crystal semiconductor layer.

In the semiconductor photo-electrically-sensitive device of such astructure, the intrinsic non-single-crystal semiconductor layer presentsphoto-conductivity corresponding to the intensity of incident light.Usually, the intrinsic non-single-crystal semiconductor layer containshydrogen or a halogen as a recombination center neutralizer forneutralization of recombination centers which would otherwise exist inlarge quantities since the intrinsic non-single-crystal semiconductorlayer is formed of a non-single-crystal semiconductor. This prevents thephoto-sensitivity of the intrinsic non-single-crystal semiconductorlayer from being lowered by recombination centers.

The photo-sensitivity of the conventional semiconductorphoto-electrically-sensitive device of this kind is very low and readilychanges with changes in the intensity of incident light or temperature.

As a result of various experiments, the present inventor has found thatone of the reasons for the low photo-sensitivity and its instability isthat in the case where the intrinsic non-single-crystal semiconductorlayer of the non-single-crystal semiconductor layer member is formedinevitably containing sodium as an impurity, the sodium content is aslarge as 10²⁰ atoms/cm³ or more.

Moreover, the present inventor has found that such a large sodiumcontent lowers the photo-sensitivity of the semiconductorphoto-electrically-sensitive device and gives rise to the instability ofthe photo-sensitivity for the following reasons:

In a case where the intrinsic non-single-crystal semiconductor layercontains sodium in as high a concentration as 10²⁰ atoms/cm³ or more, alarge number of clusters of sodium are created in the intrinsicnon-single-crystal semiconductor layer and these clusters of sodiumserve as recombination centers of photo carriers. Accordingly, when thesodium content is large as mentioned above, the intrinsicnon-single-crystal semiconductor layer contains a number ofrecombination centers of photo carriers which are not neutralized by arecombination center neutralizer. Consequently, photo carriers which aregenerated by the incidence of light in the intrinsic non-single-crystalsemiconductor layer are recombined with the recombination centers,resulting in a heavy loss of the photo carriers. Further, the intrinsicnon-single-crystal semiconductor layer, when containing sodium, createsdangling bonds of sodium, which serve as donor centers. In the casewhere the intrinsic non-single-crystal semiconductor layer containssodium in as high a concentration as 10²⁰ atoms/cm³ or more, it containsmany dangling bonds of sodium acting as donor centers. In this case, thecenter level of the energy band in the widthwise direction thereof inthe intrinsic non-single-crystal semiconductor layer relatively greatlydeviates further to the valence band than the Fermi level. Accordingly,the photosensitivity of the intrinsic non-single-crystal semiconductorlayer depending upon the intensity of light is very low and changes withthe intensity of the incident light or temperature. Further, thediffusion length of holes of the photo carriers in the intrinsicnon-single-crystal semiconductor layer is short.

Moreover, the sodium contained in the intrinsic non-single-crystalsemiconductor layer is combined with the material forming the layer. Forinstance, when the layer is formed of silicon, it has a combinationexpressed by the general formula Si--Na--Si. Accordingly, when thesodium content is as large as 10²⁰ atoms/cm³ or more, the layer containsthe combination of the material forming the layer and the sodium inlarge quantities.

The combination of the material forming the intrinsic non-single-crystalsemiconductor layer and the sodium contained therein is decomposed bythe incident light to create in the layer dangling bonds of the materialforming it and dangling bonds of the sodium.

Therefore, in the case where the intrinsic non-single-crystalsemiconductor layer contains sodium in as high a concentration as 10²⁰atoms/cm³ or more, the dangling bonds of the material forming the layerand the dangling bonds of sodium which are generated in the layer, willbe greatly increased by the incident light. In such a case, the danglingbonds of the material forming the layer act as recombination centers ofthe photo carriers, and the loss of the photo carriers generated in thelayer increases. As the dangling bonds of the sodium increase, thecenter level of the energy band in the widthwise direction thereof,which has greatly deviated further to the valence band than the Fermilevel, further deviates toward the valence band correspondingly,resulting in marked reduction of the photo carrier generating efficiencyof the intrinsic non-single-crystal semiconductor layer. Also thediffusion length of holes of the photo carriers in the intrinsicnon-single-crystal semiconductor layer is further reduced, markedlyraising the dark conductivity of the layer.

In a state in which the photo carrier generating efficiency of theintrinsic non-single-crystal semiconductor layer has thus been loweredand the loss of the photo carriers in the layer and the darkconductivity of the layer have thus been increased, if the layer isheated, the dangling bonds of the material forming the layer and thedangling bonds of sodium, generated in large quantities in the layer,will be partly combined with each other to re-form the combination ofthe material forming the layer and the sodium. As a result, both thedangling bonds of the material forming the layer and the sodium contentwill be decreased. In the intrinsic non-single-crystal semiconductorlayer, however, the dangling bonds of the material forming the layer andthe dangling bonds of sodium still remain in large quantities.Consequently, the photo carrier generating efficiency-of the intrinsicnon-single-crystal semiconductor layer is very low to impose a loss onthe photo carriers in the layer, and the dark conductivity of the layeris extremely high. In addition, the photo carrier generating efficiency,the photoconductivity, the loss of photo carriers and the darkconductivity of the intrinsic non-single-crystal semiconductor layer,and accordingly the photo-sensitivity of the layer largely differ beforeand after heating.

The above is the reason found by the present inventor for which thephoto-sensitivity of the conventional semiconductorphoto-electrically-sensitive device is low and readily varies with theintensity of incident light or temperature when the intrinsicnon-single-crystal semiconductor contains sodium in as high aconcentration as 10²⁰ atoms/cm³ or more.

Further, the present inventor has also found that when the semiconductorcontains oxygen in as high a concentration as 10²⁰ atoms/cm³ or more,the photo-sensitivity of the conventional semiconductorphoto-electrically-sensitive device is very low and fluctuates as theintensity of the incidence light or temperature fluctuates for thefollowing reason:

When the intrinsic non-single-crystal semiconductor layer containsoxygen in as high a concentration as 10²⁰ atoms/cm³ as referred topreviously, the layer forms therein a number of clusters of oxygen. Theclusters of oxygen act as combination centers of photo carriers as isthe case with the clusters of sodium. Further, the intrinsicnon-single-crystal semiconductor layer, when containing oxygen in such ahigh concentration as 10²⁰ atoms/cm³, the layer contains dangling bondsof oxygen acting as donor centers and the combination of the materialforming the layer and oxygen in large quantities. The combination of thematerial forming the layer and oxygen is decomposed by the incidentlight to create in the layer dangling bonds of the material forming itand dangling bonds of the oxygen. If the layer is heated, the danglingbonds of the material forming the layer and the dangling bonds of oxygenwill be decreased in small quantities but remain in the layer in largequantities.

The above is the reason found by the present inventor for which thephoto-sensitivity of the conventional semiconductor photoelectricconversion device is very low and varies with changes in the intensityof the incident light or temperature when the intrinsicnon-single-crystal semiconductor layer contains oxygen in as high aconcentration as 10²⁰ atoms/cm³ or more.

Moreover, the present inventor has found that when the intrinsicnon-single-crystal semiconductor layer contains sodium and oxygen eachin as high a concentration as 10²⁰ atoms/cm³ or more, too, thephoto-sensitivity of the conventional semiconductorphoto-electrically-sensitive device is very low and varies with changesin the intensity of the incident light or temperature. The reasontherefor will be apparent from the previous discussions.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a novelsemiconductor photo-electrically-sensitive device which is provided withat least a non-single-crystal semiconductor layer member having at leastone intrinsic non-single-crystal semiconductor layer and whosephoto-sensitivity is far higher and much less variable with changes inthe intensity of incident light or temperature than that of theconventional semiconductor photo-electrically-sensitive devices of theabove said construction.

In accordance with an aspect of the present invention, even if theintrinsic non-single-crystal semiconductor layer of thenon-single-crystal semiconductor layer member is inevitably formedcontaining sodium singly, or sodium and oxygen as impurities, the sodiumor sodium and oxygen contents are each as low as 5×10¹⁸ atoms/cm³ orless.

Therefore, the photo-sensitivity of the semiconductorphoto-electrically-sensitive device of the present invention is farhigher and much less variable with changes in the intensity of incidentlight or temperature than is conventional for the semiconductorphoto-electrically-sensitive devices of this kind.

For the following reason ascertained by the present inventor for thefirst time, the photo-electrically-sensitive device of the presentinvention in the case of the sodium content being 5×10¹⁸ atoms/cm³ orless is far higher and much less variable with changes in the intensityof the incident light or temperature than the photo-sensitivity of theconventional photo-electrically-sensitive device in the case of thesodium content being 10²⁰ atoms/cm³ or more as described previously.

When the sodium content of the intrinsic non-single-crystalsemiconductor layer is 5×10¹⁸ atoms/cm³ or less, there is formed in thelayer substantially no or a very small number of clusters of sodiumwhich act as recombination centers of photo carriers. Accordingly, theintrinsic non-single-crystal semiconductor layer has substantially no ora very small number of recombination centers of photo carriers based onsodium. This means that substantially no or a very small of loss isimposed on the photo carriers that are created in the intrinsicnon-single-crystal semiconductor layer.

With the above sodium content in the intrinsic non-single-crystalsemiconductor layer, the number of dangling bonds of sodium contained inthe layer is very small, even if some bonds are so therein contained. Inthis instance, the center level of the energy band in the widthwisedirection of the intrinsic non-single-crystal semiconductor layer hardlydeviates from the Fermi level and even if it deviates, the amount ofdeviation is very small. Consequently, the photo carrier generatingefficiency is far higher than is obtainable with the conventionalsemiconductor photo-electrically-sensitive device in which the sodiumcontent of the intrinsic non-single-crystal semiconductor layer is 10²⁰atoms/cm³ or more, and the dark conductivity of the layer is far lowerthan in the case of the prior art device.

Further, when the sodium content in the intrinsic non-single-crystalsemiconductor layer is 5×10¹⁸ atoms/cm³ or less, even if the layercontains combinations of the material foiling the layer and the sodium,the number of such combinations is very small. Accordingly, danglingbonds of the material forming the layer and sodium are not substantiallyformed by the light irradiation of the semiconductor photo-electricallysensitive device and, even if they are formed, their numbers are verysmall. Moreover, even if the device is heated, the dangling bonds of thelayer material and to sodium will not increase. The photo carriergenerating efficiency, the photo conductivity and the dark conductivityand accordingly the photo-sensitivity of the layer will remainsubstantially unchanged before and after irradiation by light and afterheating.

For the reasons given above, when the sodium content in the intrinsicnon-single-crystal semiconductor layer is 5×10¹⁸ atoms/cm³ or less, thesemiconductor photo-electrically-sensitive device of the presentinvention exhibits a far higher and stable photosensitivity than theconventional semiconductor photo-electrically-sensitive device in whichthe sodium content in the intrinsic non-single-crystal semiconductorlayer is 10²⁰ atoms/cm³ or more.

For the same reasons as mentioned above, the photo-sensitivity of thephoto-electrically-sensitive device of the present invention in the caseof the oxygen content being 5×10¹⁸ atoms/cm³ or less is far higher andmuch less variable with changes in the intensity of incident light ortemperature than the photo-sensitivity of thephoto-electrically-sensitive device in the case of the oxygen contentbeing 10²⁰ atoms/cm³ or more as described previously. Therefore, nodetailed description will be given thereof.

Additionally, the reason for which the photo-sensitivity of thephoto-electrically-sensitive device in the case of the sodium and oxygencontents each being 5×10¹⁵ atoms/cm³ or less is far higher and much lessvariable with changes in the intensity of incident light or temperaturethan the photo-sensitivity of the photo-electrically-sensitive device inthe case of the sodium and oxygen contents each being 10²⁰ atoms/cm³ ormore as referred to previously is the same reason as mentioned above.Therefore, no detailed description will be given thereof.

The semiconductor material formed in accordance with the presentinvention is applicable not only to photoelectric conversion devices,but also to other semiconductor devices which utilize an intrinsic orsubstantially intrinsic non-single crystalline semiconductor layer.

Other objects, features and advantages of the present invention willbecome more fully apparent from the following detailed description takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2, 3 and 4 are schematic cross-sectional views respectivelyillustrating first, second, third and fourth embodiments of asemiconductor photo-electrically-sensitive device to which the presentinvention is applicable;

FIG. 5 is a diagram showing the distribution of sodium in the depthwisedirection of the intrinsic non-single-crystal semiconductor layer of anon-single-crystal semiconductor layer member in the semiconductorphoto-electrically-sensitive device depicted in FIGS. 1 to 4, usingdifferent kinds of substrates;

FIG. 6 is a diagram showing variations in the photo-sensitivity of theintrinsic non-single-crystal semiconductor layer of thenon-single-crystal semiconductor layer member in the semiconductorphoto-electrically-sensitive devices depicted in FIGS. 1 to 4 when thelayer was irradiated by light and then heated, using different kinds ofsubstrates;

FIG. 7 is a diagram showing variations in rated quantum efficiency withrespect to the wavelength of incident light in the semiconductorphoto-electrically-sensitive devices depicted in FIGS. 3 to 4 when theywere irradiated by light and then heated; and

FIG. 8 is a diagram, similar to FIG. 7, showing variation in ratedquantum efficiency in a conventional semiconductorphoto-electrically-sensitive device which is seemingly identical inconstruction with the devices shown in FIG. 3 and 4.

FIG. 9 is an example of an IG-FET having a non-single crystallinesemiconducting material of an intrinsic or substantially intrinsicconductivity type.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1, 2, 3 and 4 illustrate first, second, third and fourthembodiments of the semiconductor photo-electrically-sensitive devices towhich the present invention is applicable.

The first embodiment of the semiconductor photo-electrically-sensitivedevice shown in FIG. 1 has such a construction as follows:

A light transparent insulating substrate 1 has conductive layer 2 and 3of, for example, tin oxide. The light transparent substrate 1 is made ofglass, fused quartz, synthetic quartz, or the like.

On the light transparent substrate 1 is formed a non-single-crystalsemiconductor layer member 4. The non-single-crystal semiconductor layermember 4 has an intrinsic non-single-crystal semiconductor layer 5containing hydrogen or a halogen as recombination center neutralizer.The intrinsic non-single-crystal semiconductor layer 5 is formed ofsilicon (Si), germanium (Ge), Si_(x) Ge_(1-x), or the like. The layer 5has a thickness of, for example, 0.5 um.

The intrinsic non-single-crystal semiconductor layer 5 making up thenon-single-crystal semiconductor layer member 4 is formed by a CVDmethod which does not employ a glow discharge technique, or a plasma CVDmethod which employs the glow discharge technique.

The second embodiment of the semiconductor photo-electrically-sensitivedevice shown in FIG. 2 has such a construction as follows:

The second embodiment of the semiconductor photo-electrically-sensitivedevice has the same structure as does the first embodiment of thesemiconductor photo-electrically-sensitive device shown in FIG. 1 exceptthat the conductive layers 2 and 4 are formed on the non-single-crystalsemiconductor layer member 4. Therefore, no detailed description will berepeated.

The third embodiment of the semiconductor photoelectric conversiondevice shown in FIG. 3 has such a construction as follows:

A light transparent conductive layer 12 of tin oxide is formed, forexample, by vacuum deposition on an insulating and light transparentsubstrate 1 of glass, fused quartz, synthetic quartz, or the like. Onthe conductive layer 12 is formed a lead 13 thereof.

On the light transparent conductive layer 12 is formed anon-single-crystal semiconductor layer member 4. The non-single-crystalsemiconductor layer member 4 is formed by a sequential lamination of,for instance, a P-type non-single-crystal semiconductor layer 14, anintrinsic non-single-crystal semiconductor layer 5 containing hydrogenor a halogen as recombination center neutralizer, and an N-typenon-single-crystal semiconductor layer 16. Accordingly, thenon-single-crystal semiconductor layer member 4 has one intrinsicnon-single-crystal semiconductor layer 5 and has formed therein one PINjunction. In this case, the P-type non-single-crystal semiconductorlayer 14 is formed of silicon (Si), Si_(x) C_(1-x) (0<x<1) where x=0.8,for instance), germanium (Ge) or the like, and the layer 14 is, forinstance, 100 A thick. When the P-type non-single-crystal semiconductorlayer 14 is formed of silicon of Si_(x) C_(1-x), the intrinsicnon-single-crystal semiconductor layer 5 is formed of silicon or Si_(x)Ge_(1-x), and when the layer 14 is formed of germanium, the layer 5 isalso formed of germanium. The layer 5 has a thickness of, for example,0.5 um. Further, when the intrinsic non-single-crystal semiconductorlayer 5 is formed of silicon or Si_(x) Ge_(1-x), the N-typenon-single-crystal semiconductor layer 16 is formed of silicon of Si_(x)C_(1-x) (x=0.9, for example), and when the layer 5 is formed ofgermanium or Si_(x) Ge_(1-x), the layer 16 is also formed of germaniumor Si_(x) Ge_(1-x). The N-type non-single-crystal semiconductor layer 16is, for example, 200 Ain thickness.

The non-single-crystal semiconductor layers 14, 15 and 16 making up thenon-single-crystal semiconductor layer member 4 are successively formedby the CVD method which does not employ the-glow discharge technique, ora plasma CVD method which employs the glow discharge technique.

On the non-single-crystal semiconductor layer member 4 is formed, forexample, by vacuum deposition on a reflecting conductive layer 17 as ofaluminum (Al).

The fourth embodiment of the semiconductor photoelectric conversiondevice shown in FIG. 4 has such a construction as follows:

On a reflecting conductive substrate 21 as of stainless steel is formedthe non-single-crystal semiconductor layer member 4 as is the case withthe semiconductor photo-electrically-sensitive device shown in FIG. 3.

The non-single-crystal semiconductor layer member 4 is formed by asequential lamination of the P-type non-single-crystal semiconductorlayer 14, the intrinsic non-single-crystal semiconductor layer 5containing hydrogen or a halogen as a recombination center neutralizerand the P-type non-single-crystal semiconductor layer 16 as is the casewith the non-single-crystal semiconductor layer member 4 in FIG. 3.Accordingly, the non-single-crystal semiconductor layer member 4 has oneintrinsic non-single-crystal semiconductor layer 5 and has formedtherein one PIN junction as is the case with the non-single-crystalsemiconductor layer member 4 in FIG. 3. The non-single-crystalsemiconductor layer 14, 15 and 16 are also formed by such a CVD methodas mentioned above.

On the non-single-crystal semiconductor layer member 4 is formed, forinstance, by vacuum deposition a light transparent conductive layer 22as of indium oxide containing tin oxide, which corresponds to theconductive layer 12 in FIG. 3

Further, a conductive layer 23 for external connection is formed on theconductive layer 23.

The first and second embodiments shown in FIGS. 1 and 2 are apparentlyidentical in construction with a known semiconductor photo detector. Thethird and fourth embodiments of FIGS. 3 and 4 are apparently identicalin construction with known semiconductor photoelectric conversiondevices.

With each of the structures of the semiconductorphoto-electrically-sensitive devices shown in FIGS. 1 and 2, when light8 impinges on the device from the outside, the non-single-crystalsemiconductor layer member 4 becomes conductive. Accordingly, if a loadis connected across the conductive layer 2 and 3 through a power supply(not shown), power is supplied to the load.

With the structure of the semiconductor photo-electrically-sensitivedevice shown in FIG. 3, when light 8 impinges on the device from theoutside of the substrate 11, it reaches the intrinsic non-single-crystalsemiconductor layer 5 of the non-single-crystal semiconductor layermember 4, creating therein photo carriers. Accordingly, if a load isconnected across the light transparent conductive layer 12 and thereflecting conductive layer 12, power is supplied to the load.

With the structure of the semiconductor photo-electrically-sensitivedevice of FIG. 4, the light 8 incident to the light transparentconductive layer 22 reaches the non-single-crystal semiconductor layer 5of the non-single-crystal semiconductor layer member 4 to therebygenerate therein photo carriers as is the case with the device shown inFIG. 3. Accordingly, if a load is connected across the reflectingconductive substrate 21 and the light transparent conductive layer 22,power is supplied to the load.

Where the transparent substrate 1 is an ordinary glass substrate, itcontains sodium in large quantities, therefore, the intrinsicnon-single-crystal semiconductor layer 5 of the non-single-crystalsemiconductor layer member 4 formed by the CVD method on the substrate 1inevitably contains sodium in large quantities. The same is true of thecase where the substrate 1 is made of fused quartz as well. In thisinstance, however, since the sodium content in the substrate 1 issmaller than in the case of ordinary glass, the sodium content in theintrinsic non-single-crystal semiconductor layer is smaller than in thecase of the substrate of the ordinary glass. It is to be noted that whenthe substrate 1 is made of synthetic quartz, since its sodium content isvery small, the intrinsic non-single-crystal semiconductor layer formedthereon contains a very small amount of sodium.

Furthermore, when the intrinsic non-single-crystal semiconductor layer 5of the semiconductor photo-electrically-sensitive device depicted inFIG. 1, 2, 3, or 4 is deposited by the CVD process, if sodium componentsstick to the inner walls of a reaction chamber used therefor (thesubstrate, the substrate holder and so on) the intrinsic layer 5 willinevitably contain sodium in large quantity.

When the intrinsic non-single-crystal semiconductor layer 5 of thenon-single-crystal semiconductor layer member 4 is formed of silicon bythe CVD method using, for example, silane (SiH₄) gas as a semiconductormaterial gas it inevitably contains oxygen. The reason is that it isextremely difficult to remove oxygen from the silane gas when it isprepared. Incidentally, commercially available silane gas of 99.99%purity usually contains oxygen about 0.1 ppm in the form of a simplesubstance (O₂) and about 3 ppm in the form of water (H₂ O), carbon about5 ppm in the form of methane (CH₄) and about 0.1 ppm in the form ofethane (C₂ H₆), ethylene (C₂ H₄), propane C₃ H₈) and propylene (C₃ H₆)and phosphorus about 0.1 ppm in the form of phosphine (PH₃).

Further, when the intrinsic non-single-crystal semiconductor layer 5 ofthe non-single-crystal semiconductor laminate member 3 is formed ofgermanium by the CVD method using, for example, germane (GeH₄) gas asthe semiconductor material gas, the layer 5 inevitably contains oxygenbecause it is extremely difficult, in practice, to remove it from thegermane gas when it is prepared.

Moreover, when the intrinsic non-single-crystal semiconductor layer 5 ofthe non-single-crystal semiconductor laminate member 3 is formed ofSi_(x) Ge_(1-x) by the CVD method using, as the semiconductor materialgas, a mixture of silane and germane gases, the layer 5 inevitablycontains oxygen because it is extremely difficult, in practice, toprepare the silane and germane gases with substantially no oxygencontent.

In the conventional photoelectric device similar to those of FIGS. 1 to2, the intrinsic non-single-crystal semiconductor layer 5 of thenon-single-crystal semiconductor layer member 4 contains sodium andoxygen each in a high concentration exceeding 10²⁰ atoms/cm³.

In contrast thereto, according to the present invention, even if theintrinsic non-single-crystal semiconductor layer 5 of thenon-single-crystal semiconductor laminate member 4 inevitably containssodium and oxygen, the sodium and oxygen contents are each only 5×10¹⁸atoms/cm³ or less.

The intrinsic non-single-crystal semiconductor layer with such a smallsodium content can be formed by pretreating or cleaning the reactionchamber for removing therefrom sodium and by using a substratecontaining only a negligibly small amount of sodium. If the sodiumcontent in the substrate is relatively large, it is necessary only topretreat or clean the substrate and the substrate holder for removingthe sodium. The removal of sodium from the reaction chamber can beachieved in such a manner as follows: First, gas containing a chloride,for example, a gas mixture of oxygen and hydrogen chloride, isintroduced into the reaction chamber and then the reaction chamber isheated at, for instance, about 1150 C. so that the gas reacts with thesodium to render it into NaCl gas. Thereafter, the reaction chamber issufficiently evacuated.

The removal of sodium from the substrate and the substrate holder can beattained by the same method as described above, after placing them inthe reaction chamber.

The intrinsic non-single-crystal semiconductor layer 5 with a smalloxygen content can be formed by using, as the semiconductor material gasfor forming the layer of silicon through the CVD method as mentionedabove, silane gas which is obtained by passing raw silane gas of highpurity through a passage in which is placed a molecular sieve having amesh diameter of 2.7 to 4.65 A or zeolite having the same pore diameterso that the oxygen content of the silane gas may be reduced tosubstantially zero or negligibly small. The reason for which such silanegas with practically no or a negligibly small amount of oxygen can beobtained from the raw silane gas through use of the molecular sieve orzeolite, is as follows:

The effective molecular diameter of the silane is larger than 4.65 A andwhen oxygen is contained as of O₂ and H₂ O in the raw silane gas asreferred to previously, their molecular diameters are in the range offrom 2.7 to 4.65 A, so that the silane cannot pass through the meshes ofthe molecular sieve or the pores of the zeolite and hence is notabsorbed on the molecular sieve or zeolite, whereas the oxygen and watercontained in the raw silane gas pass through the meshes of the molecularsieve or the pores of the zeolite and are effectively absorbed thereon.

The oxygen content of such silane gas can be further reduced by passingit through a passage in which a deoxidizing agent is placed. By usingthe thus obtained silane gas, the oxygen content of the intrinsicnon-single-crystal semiconductor layer 5 can be further reduced.

According to the present invention, the intrinsic non-single-crystalsemiconductor layer 5 contains sodium in a low concentration of 5×10¹⁸atoms/cm³ or less and oxygen in a low concentration of 5×10¹⁵ atoms/cm³or less.

Therefore, according to the embodiments of the present invention shownin FIGS. 1 to 4, the photo-sensitivity of the intrinsicnon-single-crystal semiconductor layer 5 is higher than thephoto-sensitivity of the intrinsic non-single-crystal semiconductorlayer of the conventional photo-electrically-sensitive device whichcontains each of sodium and oxygen in a high concentration of 10₂₀atoms/cm³ or more.

FIGS. 5 to 8 show the above.

That is to say, when the intrinsic non-single-crystal semiconductorlayer 5 of the non-single-crystal semiconductor layer member 4 isdeposited on an ordinary glass substrate of a large sodium contentthrough the CVD method in the reaction chamber from which sodium hasbeen removed according to the present invention, if the substrate hasnot been cleaned for removing sodium as referred to above, then sodiumwill be distributed in the intrinsic non-single-crystal semiconductorlayer 5 depthwise thereof as indicated by the curve A in FIG. 5. Also inthe case of similarly forming the layer 5 on a fused quartz substrate ofa relatively large sodium content in the sodium-free reaction chamber,if the substrate has not been cleaned, then sodium will be distributedin the layer 5, as indicated by the curve B in FIG. 5. However, in thecase of similarly forming the layer 5 on a synthetic quartz substrate ofa very small sodium content through the CVD method in the cleanedreaction chamber, the layer 5 will have such a distribution of sodium asindicated by the curve C in FIG. 5.

Where the layer 5 has such a distribution of sodium as indicated by thecurve A in FIG. 5, it presents such photo-conductivity as plotted bypoints A0, A2, A4 . . . and such dark conductivity as plotted by pointsA0', A2', A4' . . . in FIG. 6. The point A0 and A0' show the initialphoto-conductivity and dark conductivity of the layer 5. The points A2and A2' indicate photo-conductivity and dark conductivity after twohours of irradiation of the layer 5 by light under AM1 radiationcondition (100 mW/cm²) at room temperature. The points A4 and A4' showthe photo-conductivity and dark conductivity of the layer 5 heated at150° C. for two hours thereafter. The points A6 and A6', A8 and A8' . .. show similar photoconductivity and dark conductivity at respectivepoints of time.

Where the intrinsic layer 5 has the sodium distribution indicated by thecurve B in FIG. 5, it exhibits such photo-conductivity as plotted bypoints B0, B2, B4, . . . corresponding to the above-mentioned A0, A2,A4, . . . and such dark conductivity as plotted by points B0', B2', B4',. . . corresponding to the above mentioned A0', A2', A4', . . . in FIG.6.

Where the intrinsic layer 5 has the sodium distribution indicated by thecurve C in FIG. 5, it presents such photo-conductivity as plotted bypoints C0, C2, C4, . . . corresponding to the above-mentioned A0, A2,A4, . . . and such dark conductivity as plotted by points C0', C2', C4',. . . corresponding to the above-mentioned A0', A2°, A4', . . . in FIG.6.

The values of photo-conductivity between the points A0 and A0', betweenA2 and A2', between A4 and A4', . . . between the points B0 and B0',between B2 and B2', between B4 and B4', . . . , and between C4 and C4',. . . respectively show photo-sensitivity. Furthermore, the value ofphotoconductivity A2 and A3, . . . , between the points B0 and B2,between B2 and B3, and between the points C0 and C2, between C2 and C4,. . . respectively show the deviation of the photo-conductivity.

Where the intrinsic layer 5 has such a sodium distribution as indicatedby the curve C in FIG. 5 according to the present invention, thesemiconductor photo-electrically-sensitive devices depicted in FIGS. 3and 4 exhibits, relative to the wavelength of the incident light 8, suchrated quantum efficiencies as indicated by the curves D0, D2, and D4 inFIG. 7. The curves D0, D2, and D4 respectively show rated quantumefficiencies in the cases corresponding to those where the points A0 andA0', A2 and A2', and A4 and A4' in FIG. 6 are obtained.

Where the intrinsic layer 5 has the sodium distribution indicated by thecurve A in FIG. 5 not according to the present invention, thesemiconductor photo-electrically-sensitive devices shown in FIGS. 3 and4 present rated quantum efficiencies indicated by the curves E0, E2, andE4 in FIG. 8 respectively corresponding to the curves D0, D2, and D4 inFIG. 7.

In the above, no reference is made to the distribution of oxygen in theintrinsic layer 5, but when the layer 5 have oxygen distributionssimilar to the sodium distributions described above in regard to FIG. 5,the same results as referred to above in connection with FIGS. 6 to 8can be obtained.

As will be appreciated from the above, according to the presentinvention the photo-sensitivity of the intrinsic layer 5 is very highand hardly changes even if heating is carried out after the irradiationby light.

While the present invention has been described as being applied to thesemiconductor photo-electrically-sensitive device in which thenon-single-crystal semiconductor layer member has a PIN or NIP typestructure and, accordingly, it has formed therein one PIN or NIPJunction, the present invention is also applicable to such asemiconductor photo-electrically-sensitive device in which thenon-single-crystal semiconductor laminate member has an NI, PI, NIN orPIP type structure and, accordingly, it has formed therein at least oneNI, PI, NIN or PIP junction.

Also the present invention is applicable to semiconductorphoto-electrically-sensitive device of the type in which thenon-single-crystal semiconductor layer member has, for example, an NIPINor PINIP type structure and, accordingly, it has formed therein at leastone PIN and NIP junction.

The semiconductor material formed in accordance with the presentinvention is applicable not only to the photoelectric conversiondevices, but also to other semiconductor devices which utilize anintrinsic or substantially intrinsic non-single-crystallinesemiconductor layer. Substantially intrinsic means that thesemiconductor layer contains impurities having a valence of three orfour for example B or P at a concentration of 1×10¹⁸ atoms/cm³ or less.

An example of such semiconductor devices is an IG-FET as shown in FIG.9. In the IG-FET of FIG. 9, a gate electrode 202 of the IG-FET is formedon a substrate 201 while the insulating layer 203 is formed over thesubstrate 201 and gate electrode 202. Formed on the insulating layer 203is a semiconducting channel layer 204 and formed on the channel layer204 is a semiconductor layer 205, 206 from which the source 205 anddrain 206 are formed. In accordance with the present invention, thechannel layer 4 comprises a non-single-crystalline semiconductingmaterial of an intrinsic or substantially intrinsic conductivity type,which contains sodium or oxygen in a low concentration f only 5×10¹⁸atoms/cm³ or less, respectively.

It will be apparent that many modifications and variations may beeffected without departing from the scope of the novel concepts of thepresent invention.

I claim:
 1. A non-single-crystalline semiconductor material comprisingsilicon having at least one junction formed between a substantiallyintrinsic semiconductor material and a one conductivity typesemiconductor material, said junction being one of NI, PI, PIN, PIP, andNIN junctions wherein at least said substantially intrinsicsemiconductor material has added thereto at least one of a halogen andhydrogen as a dangling bond neutralizer and contains sodium in aconcentration of 5×10¹⁸ atoms/cm³ or less.
 2. The semiconductor materialof claim 1 wherein said one conductivity type semiconductor materialcontains an impurity having a valence of three or five at aconcentration of 1×10¹⁸ atoms/cm³ or less.
 3. The semiconductor materialof claim 2 wherein said impurity is B or P.
 4. The semiconductormaterial of claim 1 wherein at least said substantially intrinsicsemiconductor material contains oxygen in a concentration of 5×10¹⁸atoms/cm³ or less.
 5. A semiconductor device comprising:a substratehaving an insulating surface; and a non-single crystalline semiconductorlayer formed on said substrate, said layer having at least one junctionformed between a substantially intrinsic semiconductor region and a oneconductivity type semiconductor region, said junction being one of NI,PI, PIN, PIP, and NIN junctions; wherein at least said substantiallyintrinsic semiconductor region contains sodium in low concentration ofonly 5×10¹⁸ atoms/cm³ or less.
 6. The semiconductor device of claim 5wherein a conductive layer is further formed on a surface of saidnon-single-crystalline semiconductor layer.
 7. The semiconductor deviceof claim 5 wherein said semiconductor layer comprises a siliconsemiconductor.
 8. The semiconductor device of claim 5 wherein said oneconductivity type semiconductor region contains an impurity having avalence of three or five at a concentration of 1×10¹⁸ atoms/cm³ or less.9. The semiconductor device of claim 8 wherein said impurity is B or P.10. The semiconductor device of claim 5 wherein a halogen or hydrogen isadded into at least said substantially intrinsic semiconductor region asa dangling bond neutralizer.
 11. The semiconductor device of claim 5wherein at least said substantially intrinsic semiconductor regioncontains oxygen in a concentration of 5×10¹⁸ atoms/cm³ or less.
 12. Asemiconductor device comprising:a substrate having an insulatingsurface; a non-single-crystal silicon semiconductor layer formed on saidsubstrate, said layer having hydrogen or a halogen added thereto andhaving at least one junction formed between a substantially intrinsicsemiconductor region and a one conductivity type semiconductor region,said junction being one of NI, PI, PIN, PIP, and NIN junctions; whereinat least said substantially intrinsic semiconductor region containssodium in a low concentration of only 5×10¹⁸ atoms/cm³ or less.
 13. Anon-single-crystalline semiconductor material comprising silicon of asubstantially intrinsic conductivity type, wherein said semiconductormaterial is selected from the group consisting of Si, Ge, Si_(x) C_(1-x)(0<x<1), and Si_(x) Ge_(1-x) (021 x<1) and has added at thereto at leastone of a halogen and hydrogen as a dangling bond neutralizer and whereinsaid material contains sodium in a concentration of 5×10¹⁸ atoms/cm³ orless.
 14. The semiconductor material of claim 13 wherein said materialcomprises a silicon semiconductor.
 15. The semiconductor material ofclaim 13 wherein said doped layer contains an impurity having a valenceof three or five at a concentration of 1×10¹⁸ atoms/cm³ or less.
 16. Thesemiconductor material of claim 15 wherein said impurity is B or P. 17.The semiconductor material of claim 13 wherein said material containsoxygen in a concentration of 5×10¹⁸ atoms/cm³ or less.
 18. Asemiconductor device comprising:a substrate having an insulatingsurface; and a non-single crystalline semiconductor layer of anintrinsic or substantially intrinsic conductivity type formed on saidsubstrate wherein said semiconductor layer comprises a material selectedfrom the group consisting of Si, Ge, Si_(x) C_(1-x) (0<x<1), and Si_(x)(0<x<1); wherein said semiconductor layer contains sodium in a lowconcentration of only 5×10¹⁸ atoms/cm³ or less.
 19. The semiconductordevice of claim 18 wherein a conductive layer is further formed on asurface of said non-single-crystalline semiconductor layer.
 20. Thesemiconductor device of claim 18 wherein said semiconductor layercomprises a silicon semiconductor.
 21. The semiconductor device of claim18 wherein said semiconductor layer contains an impurity having avalence of three or five at a concentration of 1×10¹⁸ atoms/cm³ or less.22. The semiconductor device of claim 21 wherein said impurity is B orP.
 23. The semiconductor device of claim 18 wherein a halogen orhydrogen is added into said semiconductor layer as a dangling bondneutralizer.
 24. The semiconductor device of claim 18 wherein saidsemiconductor layer contains oxygen in a concentration of 5×10¹⁸atoms/cm³ or less.
 25. A semiconductor device comprising:a substratehaving an insulating surface; a non-single-crystal semiconductor layerformed on said substrate wherein said semiconductor layer comprises amaterial selected from the group consisting of Si, Ge, Si_(x) C_(1-x)(0<x<1), and Si_(x) Ge_(1-x) (0<x<1), said layer comprising asubstantially intrinsic non-single-crystal semiconductor in which atleast one of hydrogen and a halogen is added; wherein said semiconductorlayer contains sodium in a low concentration of only 5×10¹⁸ atoms/cm³ orless.
 26. A non-single-crystalline semiconductor device comprisingsilicon having at least one junction formed between a substantiallyintrinsic semiconductor material and a one conductivity typesemiconductor material, said junction being one of PIP and NIN junctionswherein at least said substantially intrinsic semiconductor material hasadded thereto at least one of a halogen and hydrogen as a dangling bondneutralizer and contains sodium in a concentration of 5×10¹⁸ atoms/cm³or less.
 27. A semiconductor device comprising:a substrate having aninsulating surface; and a non-single crystalline semiconductor layerformed on said substrate, said layer having at least one junction formedbetween a substantially intrinsic semiconductor region and a oneconductivity type semiconductor region, said junction being one of PIPand NIN junctions; wherein at least said substantially intrinsicsemiconductor region contains sodium in a low concentration of only5×10¹⁸ atoms/cm³ or less.
 28. A semiconductor device comprising:asubstrate having an insulating surface; a non-single-crystal siliconsemiconductor layer formed on said substrate, said layer having at leastone of hydrogen and a halogen added thereto and having at least onejunction formed between a substantially intrinsic semiconductor regionand a one conductivity type semiconductor region, said junction beingone of PIP and NIN junctions; wherein at least said substantiallyintrinsic semiconductor region contains sodium in a low concentration ofonly 5×10¹⁸ atoms/cm³ or less.
 29. A non-single-crystallinesemiconductor material having one of a NIN and PIP junctions whereinsaid semiconductor material is selected from the group consisting of Si,Ge, Si_(x) C_(1-x) (0<x<1), and Si_(x) Ge_(1-x) (0<x<1) and has addedthereto at least one of a halogen and hydrogen as a dangling bondneutralizer and wherein said material contains sodium in a concentrationof 5×10¹⁸ atoms/cm³ or less.
 30. A semiconductor device comprising:asubstrate having an insulating surface; and a non-single crystallinesemiconductor layer having one of PIP and NIN junctions formed on saidsubstrate wherein said semiconductor layer comprises a material selectedfrom the group consisting of Si, Ge, Si_(x) C_(1-x) (0<x<1), and Si_(x)Ge_(1-x) (0<x<1); wherein said semiconductor layer contains sodium in alow concentration of only 5×10¹⁸ atoms/cm³ or less.
 31. A semiconductordevice comprising:a substrate having an insulating surface; anon-single-crystal semiconductor layer formed on said substrate whereinsaid semiconductor layer has one of PIP and NIN junction and comprises amaterial selected from the group consisting of Si, Ge, Si_(x) C_(1-x)(0<x<1), and Si_(x) Ge_(1-x) (0<x<1), said layer having at least one ofhydrogen and a halogen added thereto; wherein said semiconductor layercontains sodium in a low concentration of only 5×10¹⁸ atoms/cm³ or less.32. A device as in claims 5, 12, 25, 27, 28, 30 or 31 where saidsemiconductor layer contacts an insulating surface.
 33. A device as inclaim 32 wherein a conductive element is disposed on a portion of saidinsulating surface.